Modeling a Postantibiotic World

Amesh A. Adalja, MD, FACP, FACEP, FIDSA, November 20, 2015

When the general public and policymakers are told that if the rate of antimicrobial resistance continues at its current pace we will be living in a postantibiotic world, it is not clear that they completely understand what that might mean. While most people probably understand that common infections will become more difficult to treat, they may not appreciate just how integral antibiotics are to all of modern medicine. A new study, whose senior author is Ramanan Laxminarayan from the Center for Disease Dynamics, Economics, & Policy, published in Lancet Infectious Diseases, provides a vivid description of what such a world would look like.

Antibiotic Prophylaxis

One of the cornerstones of safe surgery—from pacemaker implantations to complicated colorectal surgery—is the ability to diminish the risk of postsurgical infections by using prophylactic antibiotics. Similarly, the ability to safely administer potent cancer chemotherapy depends on the availability of antibiotics to stave off infections that may result from the reduced immunity that occurs.

The aim of this study was to quantify the impact of antibiotic resistance on the efficacy of antibiotic prophylaxis. To begin, Laxminarayan and colleagues performed a literature search to determine the absolute risk reduction for infection conferred by prophylactic antibiotic administration for the 10 most common surgeries and cancer chemotherapy. They found the overall risk of infection was 4.2% with antibiotics and 11.1% without—with wide variation depending on the specific procedure. For example, the absolute risk reduction conferred by antibiotics on colorectal surgery is 26%. When available, mortality rates of infected patients were also determined.

They next determined the current prevalence of infection-causing bacteria that are resistant to recommended prophylaxis regimens. Again, the proportion varied depending on the procedure. For example, it is estimated that 50.9% of infections after pacemaker implantation are resistant to cefazolin, the standard antibiotic used prophylactically.

Varying the Parameters

Taking this baseline data, Laxminarayan and colleagues then performed calculations and modeling based on a 30% reduction in antibiotic efficacy. The predicted results were 120,000 additional infections per year, resulting in an estimated 6,367 deaths.

The Impact of Increasing Resistance

This study is highly relevant because it quantifies the scale of the worst case scenarios engendered by antibiotic-resistant pathogens. While there are limitations inherent in such extrapolations, the results should influence the policy and clinical debates currently occurring on this issue. Effective modern healthcare is entirely dependent on our being able to perform invasive or immunity-suppressing interventions with reasonable safety. Reliably effective antibiotics are needed to ensure that safety. If patients contemplating undergoing procedures as routine as a hip replacement—let alone the much riskier prospect of cancer chemotherapy—are faced with a Russian roulette–style decision regarding the risk of contracting an antibiotic-resistant infection, it will spell the end of modern medicine.